1. Field of the Invention
This invention relates to a broadcasting receiver for vehicles, and more particularly to a receiver to be located on a vehicle capable of receiving satellite broadcasting.
2. Description of the Prior Art
A widely known conventional receiver for a vehicle to receive television broadcasting of VHF band comprises a diversity antenna combining monopole antennas mounted on a car body. This type of receivers, however, are considerably vulnerable to ghost disturbances echoed from buildings, mountains and so on. Further, as carrying cars incessantly move about from one spot to another, it is difficult to steadily assure good reception.
To solve the above problem, receivers for vehicles to steadily assure good reception irrespective of the receiving spot by receiving direct signal waves of satellite broadcasting have been proposed, for example, in Japanese Laid-open Patent Publications Nos. 260204, 260206 and 260207 of 1985 (Toku-kai-sho 60-260204, 260206 and 260207).
The proposed receivers for vehicles have common basic components as shown in FIG. 11. The receiver shown in FIG. 11 comprises a pair of bearings 12 fastened to a mounting panel 11 of a car body. The bearings 12 rotatably support a support member 13 to which a coupling box 16 is fastened. A main reflector 1 and an arm 9 are fastened to a coupling plate 7 mounted on the coupling box 16. The arm 9 extends like a fork having two prongs, with a converter 2 fastened to the tip thereof. To the support member 13 is attached a dual-pronged guide 14, with the tips of the prongs slidably fitted in guide rails 15 that are disposed parallel to each other. The coupling plate 7 mounted on the coupling box 16 permits the main reflector 1 and arm 9 to rotate through a given angle in a plane parallel to the mounting panel 11 and also to rotate through a given angle at that point in a plane perpendicular to the mounting panel 11.
When out of use, the reflector 1 and arm 9 can be collapsed toward the mounting panel 11 by turning the support member 13 in the bearings 12 and sliding the guide 14 along the guide rails 15.
When put to use, the horizontal and vertical position of the main reflector 1 are fixed by erecting the support member 13 and turning the coupling plate 7 horizontally and vertically as desired with respect to the coupling box 16. The main reflector 1 thus horizontally and vertically positioned focuses radio waves from a broadcasting satellite to the converter 2. The radio waves admitted into a primary radiator in the converter 2 are converted by a circular-linear polarizer therein. The converter then converts signals of the 12 GHZ band into BS-IF signals of the 1 GHZ band, thus completing the reception of satellite broadcasting.
Collapsing the main reflector 1 and arm 9 out of use toward the mounting panel 11 by turning the support member 13 keeps the antenna assembly from getting damaged by the wind pressure and other external forces to which the assembly is likely to be exposed while traveling.
With the conventional receivers for vehicles of the proposed type, the arm 9 must be pronged to have enough strength to carry the considerably heavy converter 2 at the tip thereof. Also, the coupling plate 7 and supporting member 13 must be large enough to withstand the large moment set up by the converter 2 and arm 9. Furthermore, large enough driving force corresponding to such large moment to set the main reflector in the desired horizontal and vertical positions in use and turn the support member 13 for collapsing the assembly out of use. Motorpowered automatic drive requires a motor of large capacity, which, in turn, increases not only power consumption but also the size of the whole assembly.
Even in the collapsed condition, a considerably large portion of the antenna stands up from the mounting panel, with not a few components thereof remaining bare and exposed. Therefore, the antenna assembly is exposed to the wind pressure when the car is running and some part or parts thereof might get hit and damaged by some obstacle. Moreover, a signals transmitting cord connecting the converter to the inside of the vehicle would be easily damaged by repeated twisting actions brought by the rotation of the antenna.